Apple Events from sandboxed apps is typically done with Apple Script. There is documentation for the entitlement needed here:
To find which app provides access groups is a bit of a hassle and there aren't many available. Use terminal and sdef
to find out. this will give you an XML which you can read and look for access-group
eg in Console:
sdef /Applications/Mail.app > mail.sdef.xml
open mail.sdef.xml
Then you'll see the line
<access-group identifier="com.apple.mail.compose" access="rw"/>